The precision of a measurement is the smallest resolvable change. The accuracy of a measurement is how close the measurement is to the true value. The two are not the same.
An example of the problem to be solved is generating a high precision, high accuracy, time-of-day measurement, given two clocks. One is an accurate clock, but it only ticks at widely spaced intervals. This clock can sometimes be unpredictably resynchronized with a master clock, so causing step changes in the time. The other is a clock which ticks rapidly, but the time given is not directly related to the first clock, and that the actual rate it counts can drift from its nominal rate. It can also stop for unpredictable periods, for example if someone else uses it. The user wants a clock which gives the right time, but also ticks rapidly, allowing accurate measurements of short time intervals. The problem is to use both clocks to generate such information.